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rocksdb/env/unique_id_gen.cc

163 lines
5.1 KiB

// Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#include "env/unique_id_gen.h"
#include <algorithm>
#include <array>
#include <cstring>
#include <random>
#include "port/port.h"
#include "rocksdb/env.h"
#include "rocksdb/version.h"
#include "util/hash.h"
namespace ROCKSDB_NAMESPACE {
namespace {
struct GenerateRawUniqueIdOpts {
Env* env = Env::Default();
bool exclude_port_uuid = false;
bool exclude_env_details = false;
bool exclude_random_device = false;
};
// Each of these "tracks" below should be sufficient for generating 128 bits
// of entropy, after hashing the raw bytes. The tracks are separable for
// testing purposes, but in production we combine as many tracks as possible
// to ensure quality results even if some environments have degraded
// capabilities or quality in some APIs.
//
// This approach has not been validated for use in cryptography. The goal is
// generating globally unique values with high probability without coordination
// between instances.
//
// Linux performance: EntropyTrackRandomDevice is much faster than
// EntropyTrackEnvDetails, which is much faster than EntropyTrackPortUuid.
struct EntropyTrackPortUuid {
std::array<char, 36> uuid;
void Populate(const GenerateRawUniqueIdOpts& opts) {
if (opts.exclude_port_uuid) {
return;
}
std::string s;
port::GenerateRfcUuid(&s);
if (s.size() >= uuid.size()) {
std::copy_n(s.begin(), uuid.size(), uuid.begin());
}
}
};
struct EntropyTrackEnvDetails {
std::array<char, 64> hostname_buf;
int64_t process_id;
uint64_t thread_id;
int64_t unix_time;
uint64_t nano_time;
void Populate(const GenerateRawUniqueIdOpts& opts) {
if (opts.exclude_env_details) {
return;
}
opts.env->GetHostName(hostname_buf.data(), hostname_buf.size())
.PermitUncheckedError();
process_id = port::GetProcessID();
thread_id = opts.env->GetThreadID();
opts.env->GetCurrentTime(&unix_time).PermitUncheckedError();
nano_time = opts.env->NowNanos();
}
};
struct EntropyTrackRandomDevice {
using RandType = std::random_device::result_type;
static constexpr size_t kNumRandVals =
/* generous bits */ 192U / (8U * sizeof(RandType));
std::array<RandType, kNumRandVals> rand_vals;
void Populate(const GenerateRawUniqueIdOpts& opts) {
if (opts.exclude_random_device) {
return;
}
std::random_device r;
for (auto& val : rand_vals) {
val = r();
}
}
};
struct Entropy {
uint64_t version_identifier;
EntropyTrackRandomDevice et1;
EntropyTrackEnvDetails et2;
EntropyTrackPortUuid et3;
void Populate(const GenerateRawUniqueIdOpts& opts) {
// If we change the format of what goes into the entropy inputs, it's
// conceivable there could be a physical collision in the hash input
// even though they are logically different. This value should change
// if there's a change to the "schema" here, including byte order.
version_identifier = (uint64_t{ROCKSDB_MAJOR} << 32) +
(uint64_t{ROCKSDB_MINOR} << 16) +
uint64_t{ROCKSDB_PATCH};
et1.Populate(opts);
et2.Populate(opts);
et3.Populate(opts);
}
};
void GenerateRawUniqueIdImpl(uint64_t* a, uint64_t* b,
const GenerateRawUniqueIdOpts& opts) {
Entropy e;
std::memset(&e, 0, sizeof(e));
e.Populate(opts);
Hash2x64(reinterpret_cast<const char*>(&e), sizeof(e), a, b);
}
} // namespace
void GenerateRawUniqueId(uint64_t* a, uint64_t* b, bool exclude_port_uuid) {
GenerateRawUniqueIdOpts opts;
opts.exclude_port_uuid = exclude_port_uuid;
assert(!opts.exclude_env_details);
assert(!opts.exclude_random_device);
GenerateRawUniqueIdImpl(a, b, opts);
}
#ifndef NDEBUG
void TEST_GenerateRawUniqueId(uint64_t* a, uint64_t* b, bool exclude_port_uuid,
bool exclude_env_details,
bool exclude_random_device) {
GenerateRawUniqueIdOpts opts;
opts.exclude_port_uuid = exclude_port_uuid;
opts.exclude_env_details = exclude_env_details;
opts.exclude_random_device = exclude_random_device;
GenerateRawUniqueIdImpl(a, b, opts);
}
#endif
SemiStructuredUniqueIdGen::SemiStructuredUniqueIdGen() : counter_{} {
saved_process_id_ = port::GetProcessID();
GenerateRawUniqueId(&base_upper_, &base_lower_);
}
void SemiStructuredUniqueIdGen::GenerateNext(uint64_t* upper, uint64_t* lower) {
if (port::GetProcessID() == saved_process_id_) {
// Safe to increment the atomic for guaranteed uniqueness within this
// process lifetime. Xor slightly better than +. See
// https://github.com/pdillinger/unique_id
*lower = base_lower_ ^ counter_.fetch_add(1);
*upper = base_upper_;
} else {
// There must have been a fork() or something. Rather than attempting to
// update in a thread-safe way, simply fall back on GenerateRawUniqueId.
GenerateRawUniqueId(upper, lower);
}
}
} // namespace ROCKSDB_NAMESPACE